Conventionally, silver paste has been used to bond a semiconductor chip to a lead frame or an electrode member in the step of producing a semiconductor device. The treatment for the sticking is conducted by coating a paste-form adhesive on a die pad of a lead frame, or the like, mounting a semiconductor chip on the die pad, and then setting the paste-form adhesive layer.
However, about the paste-form adhesive, the amount of the coated adhesive, the shape of the coated adhesive, and on the like are largely varied in accordance with the viscosity behavior thereof, a deterioration thereof, and on the like. As a result, the thickness of the formed paste-form adhesive layer becomes uneven so that the reliability in strength of bonding a semiconductor chip is poor. In other words, if the amount of the paste-form adhesive coated on an electrode member is insufficient, the bonding strength between the electrode member and a semiconductor chip becomes low so that in a subsequent wire bonding step, the semiconductor chip is peeled. On the other hand, if the amount of the coated paste-form adhesive is too large, this adhesive flows out to stretch over the semiconductor chip so that the characteristic becomes poor. Thus, the yield or the reliability lowers. Such problems about the adhesion treatment become particularly remarkable with an increase in the size of semiconductor chips. It is therefore necessary to control the amount of the coated paste form adhesive frequently. Thus, the workability or the productivity is deteriorated.
In this coating step of a paste-form adhesive, there is a method of coating the adhesive onto a lead frame or a forming chip by an independent operation. In this method, however, it is difficult to make the paste-form adhesive layer even. Moreover, an especial machine or a long time is required to coat the paste-form adhesive. Thus, a dicing die-bonding film which makes a semiconductor wafer to be bonded and held in a dicing step and further gives an adhesive layer, for bonding a chip, which is necessary for a mounting step is disclosed (see, for example, JP-A-60-57342).
This dicing die-bonding film has a structure wherein a adhesive layer and an adhesive layer are successively laminated on a supporting substrate. That is, a semiconductor wafer is diced in the state that the wafer is held on the adhesive layer, and then the supporting substrate is extended; the chipped works are peeled together with the adhesive layer; the peeled works are individually collected; and further the chipped works are bonded onto an adherend such as a lead frame through the adhesive layer.
In the meantime, an adhesive film for die bonding, which is used to bond a semiconductor chip, is, for example, a thermosetting film. As this thermosetting die bonding film, an adhesive film having a low melt viscosity is used in order to improve the adhesiveness of the film onto an adherend having largely differential levels on the basis of irregularity of its surface, typical examples of the adherend including a board having wiring thereon, and a semiconductor chip having wires thereon.
However, if the melt viscosity is too low, an adhesive bleeds out from the adhesive film to result in a problem that the adhesive pollutes the substrate or the semiconductor chip. On the other hand, if the melt viscosity is too high, the adhesiveness of the film onto an adherend deteriorates to result in a problem that voids are generated.
There is often a case that the die-bonding film of a dicing die-bonding film of this type is formed on the entire surface of an adhesive layer (an adhesive film) due to limitation of its manufacturing step. However, in such case, there has been a case that the dicing ring is contaminated because the dicing ring is adhered to the die-bonding film. On the other hand, a method in which the die-bonding film is formed into the same shape as a shape of a work piece on the pressure-sensitive adhesive layer by matching the shape of the work piece. However, in such a case, there is a case that air bubbles (voids) are generated between the die-bonding film and the chip and between the die-bonding film and the adherent during die bonding. As a result, it becomes a cause of generating troubles in a produced semiconductor device.
Therefore, a dicing die-bonding film having a die-bonding film having a high surface free energy has been used in order to improve adhesion (embedding properties) into the adherent during die bonding. However, because the surface free energy is high, the adhesion with the dicing film is improved, and thus, the die-bonding film and the dicing film cannot be peeled in the pickup step, and there is a problem that the pickup cannot be performed.
Patent Document 1 Japanese Patent Application Laid-Open No. 60-57342